Embedded polymerization driven asymmetric PEM for direct methanol fuel cells

This work reports the fabrication of proton exchange membranes (PEM) with stronger resistance to methanol penetration than Nafion^®117. A three-component acrylic polymer blend (TCPB) consisting of a copolymer of 4-vinylphenol-methyl methacrylate, poly(butyl methacrylate) (PBMA) and a copolymer of methyl methacrylate-ethyl acrylate is used as the methanol barrier. In order to implant a proton source phase within the membrane as homogeneously as possible, the hydrophilic monomers, 2-acrylamido-2-methyl propanesulfonic acid (AMPS), 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) dimethylacrylate (PEGDMA), are polymerized only after they have been embedded in the TCPB matrix. The embedded polymerization has resulted in an asymmetric membrane structure, in which the hydrophilic network is sandwiched by two layers of matrixes with high percentages of TCPB. As expected, this asymmetric membrane structure exhibits lower methanol uptake than Nafion^®117; and a proton conductivity in the range of 10⁻³–10⁻⁴ S/cm, which is dependent on the concentration of the sulfonic acid content. It is suggested that the two external layers in this asymmetric membrane provide primarily methanol-blocking and supporting proton-conducting properties; while the middle layer supplies protons and conserves water. This unique sandwiched PEM structure from embedded polymerization is confirmed by microstructure characterizations and by physical property measurements.     

The Copolymerization of Alkenes with Maleic Anhydride

The investigations presented deal with the experimental results of the copolymerization of maleic anhydride (MAn) with alkenes. The course of the reaction is explained by the overall rate of the copolymerization (v _Br), which correlates with the solution viscosity of the copolymer, and the dependence of the v _Br maximum on the mole ratio of the monomers at constant total monomer concentration. The use of solvents with increasing donor power leads to increased complexing of the free MAn molecules and of the MAn radical chain ends. The results demonstrate that, for low 1-alkenes, the addition of the MAn chain radical is the rate-determining step of the copolymerization. As the substituents on the olefinic double bond become larger or the double bond shifts to the 1,2-position, the addition of MAn to the hydrocarbon radical becomes more and more the rate-determining step. On the other hand, an increase of the CT complexation of the MAn polymer radical by use of donor solvents decreases the alkene addition rate.     

Preparation and Characterization of Styrene/Butyl Acrylate Emulsifier-Free Latex with 2-Acrylamido-2-Methyl Propane Sulfonic Acid as a Reactive Emulsifier

A kind of emulsifier-free latex (FL) was successfully synthesized from styrene (St) and butyl acrylate (BA) with 2-acrylamido-2-methyl propane sulfonic acid (AMPS) as a reactive emulsifier. The particle size of latex particles, stability against electrolytes, minimum film forming temperature (MFT) and water contact angle (CA) were evaluated and compared with a conventional latex (CL). Test results show that FL has larger particle size, better stability against electrolytes and lower MFT value compared with CL; higher AMPS content leads to smaller particle size and smaller water CA.     

Thermodynamics of phase equilibrium for systems containing N-isopropyl acrylamide hydrogels

Hydrogels are crosslinked polymers of hydrophilic monomers. Hydrogels can swell and shrink in aqueous solutions. The swelling behavior of hydrogels and the encountered phase behavior are of interest in many areas, e.g., in biotechnology, membrane science and controlled drug release. This contribution presents the criteria for such phase equilibria and a previously developed thermodynamic model for correlating/predicting the swelling and shrinking of hydrogels. The application of the method is demonstrated by describing the swelling equilibrium of some synthetic, non-ionic N-isopropyl acrylamide (N-IPAAm) hydrogels in aqueous solutions of sodium chloride at 298 K. Furthermore, new experimental results are presented for the degree of swelling of synthetic hydrogels that contain – besides the non-ionic monomer N-IPAAm – either a combination of a cationic comonomer (here, N-[3-(dimethylamino)propyl]methacrylamide (DMAPMA)) and an anionic comonomer (here, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS)) or a zwitterionic comonomer (here, [3-(methacryloylamino)propyl]dimethyl(3-sulfopropyl)ammonium hydroxide inner salt (MPSA)). These gels were equilibrated with aqueous solutions of sodium chloride at 298 K.     

微波等离子体引发合成P(AMPS/NIPA)新型智能凝胶及其性能

以2-丙烯酰胺-2-甲基丙磺@（AMPS）和异丙基丙烯酰胺（NIPA）为单体,通过微波等离子体引发聚合制备了新型二元智能凝胶P（AMPS／NIPA）,并对其性能进行了研究。探讨了等离子体功率及处理时间对聚合反应的影响;研究了该凝胶的温度敏感性、吸水／失水动力学和pH敏感性及其影响因素;对凝胶的组成及三维交联网络结构进行了表征。结果表明,P（AMPS／NIPA）二元智能凝胶具有高的溶胀比、很好的温度敏感性和pH敏感性以及快的智能响应速率。     

Applications of polymethacrylate-based monoliths in high-performance liquid chromatography

Monolithic columns were introduced in the early 1990s and have become increasingly popular as efficient stationary phases for most of the important chromatographic separation modes. Monoliths are functionally distinct from porous particle-based media in their reliance on convective mass transport. This makes resolution and capacity independent of flow rate. Monoliths also lack a void volume. This eliminates eddy dispersion and permits high-resolution separations with extremely short flow paths. The analytical value of these features is the subject of recent reviews. Nowadays, among other types of rigid macroporous monoliths, the polymethacrylate-based materials are the largest and most examined class of these sorbents. In this review, the applications of polymethacrylate-based monolithic columns are summarized for the separation, purification and analysis of low and high molecular mass compounds in the different HPLC formats, including micro- and large-scale HPLC modes.     

离子液体中壳聚糖/AMPS共聚交联微球的制备

与线性聚合物相比,交联聚合物因其复杂的结构而具有特殊的性能[1～3].壳聚糖是甲壳素的N-脱乙酰基产物,具有良好的生物相容性、无毒性和生物可降解性等特点[4],在食品、医药及水处理等领域中广泛应用[5～7].在实际应用中,经常将各种单体接枝到聚合物表面,由于单体的均聚反应影响接     

Review of recent advances in the preparation of organic polymer monoliths for liquid chromatography of large molecules

In recent years the use of monolithic polymers in separation science has greatly increased due to the advantages these materials present over particle-based stationary phases, such as their relative ease of preparation and good permeability. For these reasons, these materials present high potential as stationary phases for the separation and purification of large molecules such as proteins, peptides, nucleic acids and cells. An example of this is the wide range of commercial available polymer-based monolithic columns now present in the market.     

新型强阳离子交换聚合物整体柱的制备及其在奶制品中三聚氰胺测定中的应用

在内径为530 μm的石英毛细管中原位聚合得到一种新的强阳离子交换聚合物整体柱2-丙烯酰胺-2-甲基-1-丙磺酸-乙二醇二甲基丙烯酸酯聚合物(poly(AMPS-co-EDMA))整体柱,并将其作为聚合物整体柱微萃取(PMME)的萃取介质。优化N,N-二甲基甲酰胺(DMF)和聚乙二醇(PEG)致孔体系的比例,制备得到的poly(AMPS-co-EDMA)整体柱渗透性好、机械强度高且在水溶液中具有良好的稳定性。通过考察样品溶液的pH值、盐浓度和有机溶剂含量对萃取效率的影响,证明该整体柱主要通过强阳离子交换和疏水相互作用对三聚氰胺进行萃取富集。在PMME与高效液相色谱联用技术的基础上,建立了检测奶制品中三聚氰胺含量的分析方法。奶制品中三聚氰胺的检出限和定量限分别为0.09 mg/kg和0.3 mg/kg,在0.5~80 mg/kg的含量范围内具有良好的线性关系,日内、日间测定的相对标准偏差不高于7.5%。结果表明,该方法简便、快速、灵敏度高且成本低,适合于奶制品中微量三聚氰胺的检测。     

Poly(methacrylamide‐co‐2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) hydrogels: Investigation of pH‐ and temperature‐dependent swelling characteristics and their characterization

Novel poly(methacrylamide‐co‐2‐acrylamido‐2‐methyl‐ 1‐propanesulfonic acid) (poly(MAAm‐co‐AMPS)) hydrogels were synthesized by free radical polymerization of methacrylamide (MAAm) and 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) in deionized water at 60 °C by using ammonium peroxydisulfate (APS), N,N′‐methylenebisacrylamide (MBAAm) and N,N,N′,N′‐tetramethylethylenediamine (TEMED) as initiator, crosslinker, and activator, respectively. To investigate the effects of feed content on the pH‐ and temperature‐dependent swelling behavior of poly(MAAm‐co‐AMPS), molar ratio of MAAm to AMPS in feed was varied from 90/10 to 10/90. Structural characterization of gels was performed by Fourier transform infrared (FTIR) spectroscopy using attenuated total reflectance (ATR) technique. Thermal and morphological characterizations of gels were performed by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM), respectively. Although an apparent pH‐sensitivity was not observed for the poly(MAAm‐co‐AMPS) gels during the swelling in different buffer solutions, their temperature‐sensitivity became more evident with the increase in AMPS content of copolymer. Thermal stability of poly(MAAm‐co‐AMPS) gels increased with MAAm content. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010